Index: lib/MC/MCParser/AsmParser.cpp
===================================================================
--- lib/MC/MCParser/AsmParser.cpp
+++ lib/MC/MCParser/AsmParser.cpp
@@ -700,7 +700,8 @@
   // if it's a end of statement with a comment in it
   if (getTok().is(AsmToken::EndOfStatement)) {
     // if this is a line comment output it.
-    if (getTok().getString().front() != '\n' &&
+    if (getTok().getString().empty() == false &&
+        getTok().getString().front() != '\n' &&
         getTok().getString().front() != '\r' && MAI.preserveAsmComments())
       Out.addExplicitComment(Twine(getTok().getString()));
   }
Index: test/MC/AsmParser/empty-comment.s
===================================================================
--- /dev/null
+++ test/MC/AsmParser/empty-comment.s
@@ -0,0 +1,4 @@
+	#RUN: llvm-mc -preserve-comments -n -triple i386-linux-gnu < %s > %t
+	.text
+foo:
+	nop #
\ No newline at end of file